1. Field of the Invention
The present invention relates to a method for detecting the state of a blood sample contained in a test tube, and a detection apparatus using this method.
2. Description of the Related Art
When a blood sample contained in a test tube is separated into blood serum and blood clot, using a centrifugal separator, the test tube contains a silicone separation agent to enable accurate separation. FIG. 2 shows a test tube 1 containing a silicone separation agent B. When the test tube 1 is used, blood serum A and blood clot C are separated from each other in the test tube 1 by the silicone separation agent B after a centrifugal separation process, as shown in FIG. 2. Further, an air layer D is defined between the blood serum A and a plug 2 that closes the opening of the test tube 1.
To extract, for example, only the blood serum A from the blood sample that is separated into the blood serum A and blood clot C, the extraction process is executed by sticking a nozzle through the plug 2 into the blood serum A. Before extracting the blood serum A, it is necessary to accurately detect the separation position of the blood sample in the test tube 1.
In other words, to position the tip of the nozzle at the bottom of the blood serum A, it is necessary to detect the boundary e between the air layer D and blood serum A, the boundary f between the blood serum A and silicone separation agent B, the boundary g between the blood clot C and silicone separation agent B, the top position a of the blood serum A, the top position b of the silicone separation agent B, the top position d of the air layer D, and the thickness h of the plug 2.
The top position a of the blood serum A, the top position b of the silicone separation agent B and the top position d of the air layer D all vary depending upon the amount of the blood clot C deposited on the bottom of the test tube 1. Accordingly, unless the top positions a, b and d are accurately detected, the tip of the nozzle, for example, may contact the silicone separation agent B to draw the agent B when the nozzle is inserted into the test tube 1 to draw the blood serum A. Further, the insertion of the nozzle may be stopped before the tip of the nozzle reaches the bottom of the blood serum A, failing in complete extraction of the blood serum A from the test tube 1.
Jpn. Pat. Appln. KOKAI Publication No. 2002-323479 discloses a determination apparatus for automatically determining, from the outside of a test tube, the separation position of blood serum and blood clot in the tube. This determination apparatus includes a holding member that holds, upright, a test tube with a blood sample contained therein, a detection coil provided around the test tube, and a signal supply unit for supplying a measurement signal of a predetermined frequency to the detection coil.
In the determination apparatus, the detection coil and test tube are moved relative to each other, with the measurement signal supplied from the signal supply unit to the detection coil. During the movement, the level of the measurement signal is significantly changed in accordance with the position of the detection coil. More specifically, the relative permeability of a silicone separation agent that separates blood serum from blood clot greatly differs from those of blood serum and clot. Accordingly, when the relative positions of the detection coil and test tube are changed and the detection coil reaches the position corresponding to the silicone separation agent, the level of the measurement signal supplied to the detection coil changes abruptly. By detecting the point at which the level of the measurement signal changes abruptly, the separation position of blood serum and clot is magnetically determined.
In medical facilities, such as hospitals, collected blood samples are contained in test tubes. Private information, such as blood-collection dates and hours, the names, sexes, ages, etc., of persons from whom blood is collected, is indicated by barcodes. The barcodes are printed on, for example, a barcode label 3 as shown in FIG. 2. The barcode label 3 is attached to the outer surface of the test tube 1 that contains blood.
In a conventional blood-collecting system employed in hospitals, the test tube 1 with the barcode label 3 attached thereto is carried to a blood collecting room, where information is read from the barcode label 3 and displayed on a display unit. Based on the read information, each person is called to the blood-collecting room, where blood is collected from them. This system is disclosed in, for example, Japanese Patent No. 2739928.
In the determination apparatus disclosed in the Japanese KOKAI Publication, the separation position of blood serum and clot can be detected. However, it is difficult to accurately determine, for example, the top position a of the blood serum A, the top position b of the silicone separation agent B, the top position d of the air layer D, and the thickness h of the plug 2. Further, the determination apparatus is inevitably complex in structure, which raises the equipment expenses.
In the prior art, in addition to the magnetic determination means utilizing the detection coil, detection means, which utilizes light, electromagnetic waves or air pressure, is known. However, both means have large detection errors, which means that, for example, neither the top position a of the blood serum A nor the top position b of the silicone separation agent B can be accurately detected. Moreover, when the barcode label 3 is attached to the test tube 1, this makes it difficult to accurately detect the separation position of the blood serum A and blood clot C.